1. Field of Invention
This invention relates to methods and apparatus for an automatic fluid ejector alignment and performance system that has the ability to determine alignment and operation of at least one fluid ejector, and can provide various implementation methods to modify defects or errors in operation.
2. Description of Related Art
Fluid ejector systems, such as drop-on-demand liquid ink printers, including piezoelectric, acoustic, phase change wax-based or thermal printers, have at least one fluid ejector from which drops of fluid are ejected towards a receiving sheet. Within the fluid ejector, the fluid is contained in a plurality of channels. Power pulses cause the droplets of fluid to be expelled as required from orifices or nozzles at the end of the channels.
When the fluid ejector is an ink jet printhead, the fluid ejector may be incorporated into for example, a carriage-type printer, a partial width array-type printer, or a page-width type printer. The carriage-type printer typically has a relatively small printhead containing the ink channels and nozzles. The printhead can be functionally attached to a disposable ink supply cartridge. The combined printhead and cartridge assembly is attached to a carriage that is reciprocated to print one swath of information at a time, on a stationary receiving medium, such as paper or transparencies, where each swath of information is equal to the length of a column of nozzles.
Conventional printing systems step the receiving medium a distance generally equal to or less than the height of the swath to be printed, so that the next printed swath is contiguous or overlaps with the previously printed swath. When there is no data to print in large blocks, the receiving medium may be stepped a larger amount. This procedure is repeated until the entire image is printed.
Optimal performance of a fluid ejector requires the nozzles be properly aligned. When the fluid ejector is a color ink jet printhead, such as a four color printhead (CMYK), proper alignment of the various color heads is necessary and printed test patterns are generally used. Each alignment procedure, including vertical head to head alignment, horizontal head to head alignment, bi-directional alignment, and tilt alignment, requires four test pattern sets to be run for a four printhead printer. Furthermore, if the printhead carriage operates at multiple speeds, such as draft and normal, test pattern sets for some alignment procedures must be run for each speed. Manual procedures for correcting alignment require considerable user labor and are prone to user error. These procedures require the user to run the test pattern sets, visually observe the test pattern sets, visually judge the optimal test pattern set among various alternatives, and choose an adjustment value.
Automatic alignment procedures are also known. U.S. Pat. No. 6,609,777 B2 to Endo, the disclosure of which is incorporated herein by reference in its entirety, discloses technology for printing and determination of an adjustment value for correcting bi-directional misalignment of the dot recording positions. The printing apparatus includes an inspection unit that optically detects the passage of a continuous stream of ink droplets ejected from a printer nozzle. An adjustment value is determined based on the results of the performance of a forward pass test and a reverse pass test, and bi-directional misalignment can be determined without need for human observation.
Fluid ejector system's performance will also be impacted by a fluid ejector's nozzle performance. When the fluid ejector is in an ink jet printhead, fluid ejector performance may be impacted where particle contamination clogs the nozzle, where kogation of the heaters decreases drop velocity, or where damage occurs to the nozzle, such as due to resistor burn-out, or where the printhead brushes against the print medium, or where the nozzle plate becomes worn due to frequent servicing. Other factors may also impact nozzle performance. Fluid ejector performance is often determined by printing a test pattern and visually inspecting the test pattern results.
Automatic methods for detecting fluid ejector performance are also known. U.S. Pat. No. 6,454,380 B1 to Endo, the disclosure of which is incorporated herein by reference in its entirety, discloses a system for inspecting nozzles requiring the jetting of a continuous stream of ink droplets for detecting the clogging of nozzles in a printer wherein timings for printing operations for conducting the inspection are preset with respect to at least two print modes. Similarly, U.S. Pat. No. 6,585,346 B2 to Endo, the disclosure of which is incorporated herein by reference in its entirety, discloses a technique for detecting the presence or absence of inoperative nozzles by comparing a specific threshold with a time interval between successive detection pulses. Similarly, U.S. Pat. No. 6,604,807 to Murcia, the disclosure of which is incorporated herein by reference in its entirety, discloses a method for determining anomalous nozzles in an ink jet printing device.